This project deals with the anatomy of lizard epiphyseal systems and the relationship of the central nervous system to the endocranium in modern reptiles. Anatomical and morphological bases for functional differences in lizards that display varying degrees of development of the epiphyseal complex are explored. Parietal foremen closure with increasing size (age) in the lizard Anolis carolinensis cannot be compared directly to parietal foreman closure in the stem-reptile of 300 mya, Captorhinus aguiti. The ratio of brain volume of endocranial space volume is currently being quantified in 17 size ranges of the lizard Anolis carolinensis and in Alligator mississippiensis. These data will provide a first analysis fo such relationships using histological techniques. The forthcoming inforamtion is expected to extend an understanding of encephalization quotients and their application to brain evolution.